Abstract: Disclosed herein is a system for indicating via a colorimetric reaction the presence of a substance in a sample, comprising: a bottle containing a reagent and closable by a removable lid; and a label coupled to the bottle and comprising visual indicators for indicating the presence of a substance in a sample, wherein upon mixing the sample with the reagent in the bottle, the mixture changes to a particular color based on the identity of the substance in the sample, and each visual indicator is colored the color the mixture would be if a respective substance is in the sample, such that correspondence between the color of the mixture and the color of a visual indicator indicates the presence of the substance indicated by that visual indicator.